This disclosure relates to powder metallurgy. In particular, this disclosure relates to the use of silicon additions to drastically improve mechanical properties in certain aluminum alloy systems.
Powder metallurgy is well-suited for the production of high-volume parts in which the parts have relatively detailed features. In powder metallurgy, an initial powder metal is compacted in a tool and die set to form a preform. This preform is then sintered to order to fuse the particles of the powder metal to form a single body. Sintering is largely a solid state diffusion-driven process in which adjacent particles neck into one another; however, depending on the particular powder chemistry, a small amount of liquid phase may also develop that assists in the sintering and densification of the part. In any event, apart from some amount of dimensional shrinkage, the sintered part largely retains the shape of the as-compacted preform. After sintering, the sintered part may then be subjected to post-sintering processes such as, for example, forging, machining, heat treatments, and so forth in order to provide a final component with the desired shape, dimensional accuracy, and microstructure.
Despite the many advantages of powder metallurgy, because powder metal parts are produced by these processes, there is often a compromise in the mechanical qualities of the part in comparison to their wrought counterparts. For example, because a cast wrought part is fully dense, this wrought part usually exhibits superior strength properties in comparison to a sintered powder metal part having a similar chemistry. This difference can be attributable, in part, to the process used to form the components and the fact that the as-sintered part often is less than fully dense.
Hence, while powder metallurgy provides an economical process for the production of high-volume parts, there remains a need for improving the mechanical properties of the resultant sintered components.